The present invention relates to a semiconductor device having an internal gettering region and the method of making the same. More particularly, the present invention relates to a semiconductor device having at least one metal oxide semiconductor (MOS) transistor therein with a thin gettering region adjacent to but spaced from the active region of the transistor, and the method of making the same.
Wafers of single crystalline silicon used in making semiconductor devices generally contain contaminants, such as metal ions, which can adversely affect the electrical characteristics of the semiconductor device made in the wafer. In particular, these contaminants adversely affect the characteristics of MOS transistors formed in the wafer. Various techniques have been developed to remove these contaminants from at least the area where the active regions of the semiconductor device are formed. One technique used in making devices, including MOS transistors, is to grow a silicon oxide layer on the surface of the wafer in an atmosphere containing hydrogen chloride as described in U.S. Pat. No. 3,556,879, T. A. Major, issued Jan. 19, 1971, entitled METHOD OF TREATING SEMICONDUCTOR DEVICES, to remove the metal ions from the surface region of the wafer. Another technique is to coat the completed device with a protective coating containing a gettering material such as a glass containing phosphorus, as described in U.S. Pat. No. 3,465,209, T. R. Denning et al., issued Sept. 2, 1969, entitled SEMICONDUCTOR DEVICES AND METHODS OF MANUFACTURE THEREOF. A third technique is to embed a gettering material in and across the back surface of the wafer. A problem with the first two techniques is that they merely getter the surface of the wafer and do not provide much gettering for the internal portions of the wafer. Although the third technique does getter the internal portions of the wafer, this technique requires a very high concentration of the gettering material in order to getter completely across the thickness of the wafer to the active regions.